Adhesives which are thermally conductive are employed in several applications where a component has to be fixed upon a structure and where heat has to be deflected from the component. Many applications are therefore in the electronic components in heat exchangers. In particular heat exchangers like refrigerators can benefit by employing the present composition.
The object of current designs of refrigerator construction is to provide the cooled interior of the refrigerator or cabinet cooler with a volume as large as possible while at the same time provide for smooth inner walls that are easy to clean and maintain. This excludes the presence of protruding evaporator elements in the interior, as they were common in previous constructions. On the other hand, the aim is to keep energy consumption to a minimum. For this, a highly efficient heat transfer from the interior that is to be cooled to the evaporator units of a conventional refrigerator using vapor-compression refrigeration is required.
Presently, refrigerator/cabinet cooler constructions are used that have an inner shell or inner lining that allow a smooth walled design of the cooled interior. The evaporator units are arranged on the outside of said inner lining, with said evaporator units typically having the form of coils. This inner lining with the evaporator units is arranged in an outer housing, wherein the space in-between the outer housing and the inner lining is typically filed with heat insulating foam for thermal isolation. The inner lining of the refrigeration unit is commonly made of impact resistant plastics, in particular acrylonitrile butadiene styrene (ABS) terpolymers. The outer housing or the outer shell of the refrigeration unit is commonly made of plastics or thin metal plates.
EP-A-1 310 751 suggests to increase the energy efficiency of refrigerators by use of metallic films or metallized polymer films on the walls of the refrigerator unit, wherein said films are arranged internally, externally or as layers on or in the walls of the refrigerator unit.
Furthermore, it is known to arrange thin metal plates, for example aluminum plates, as heat conductive plating on the outer surface of the inner lining of the refrigerator unit. It is common to use double-sided adhesive strips or adhesive compositions to fixate said metal plates on the outer surface of the inner lining.
A drawback of this known approach is that the adhesive strips or adhesive compositions impair the heat transfer from the interior of the refrigerator unit to the evaporator units on the outer side of the inner lining.
EP-A-1 637 571 describes that said drawback can be overcome by use of thermally conductive filler materials in the adhesive compositions. These filler materials, while increasing the thermal conductivity, can cause an undesired increase in viscosity and/or impair the mechanical and adhesive properties of the composition or are too expensive to be economically useful.
There is thus still need in the art for adhesive compositions that exhibit excellent thermal conductivity while the negative effects on viscosity, mechanical properties and adhesiveness are minimized.